1. Technical Field
The present invention relates to a wireless power transmission system and a power transmission apparatus that wirelessly transmit power.
2. Description of the Related Art
During these years, wireless (noncontact) power transmission techniques for wirelessly (in a noncontact manner) transmitting power to mobile devices such as mobile phones and electric vehicles are being developed. When power is transmitted in a wireless power transmission system, communication between a power transmission apparatus and a power reception apparatus needs to be established for safety purposes.
Transmission of data from the power reception apparatus to the power transmission apparatus is performed, for example, using a load modulation method, in which a value of a load is varied using switching elements included in the power reception apparatus. By transmitting the variation in the load to the power transmission apparatus, data can be transmitted. On the other hand, in an application (e.g., radio-frequency identification (RFID)) in which data needs to be transmitted from a power transmission side to a power reception side, data can be transmitted from the power transmission apparatus to the power reception apparatus, for example, by modulating the frequency of power to be transmitted (hereinafter also referred to as “transmission power”).
Such data communication from a power reception apparatus to a power transmission apparatus and data communication from a power transmission apparatus to a power reception apparatus are disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2011-211779 and Japanese Unexamined Patent Application Publication No. 2008-206305.